Tuning means



Jan. 7, 1936.

5. TREVOR TUNING MEANS 2 Sheets-Sheet 1 Filed April 30, 1932 INVENTOR Y.BERTRAM TREVOR BY #W ATTORNEY Jan. 7, 1936.

B. TREVOR TUNING MEANS Filed April 50, 1932 2 Sheets-$heet 2 INVENTORBERTRAM TREVOR BY M ATTORNEY Patented Jan. 7, 1936 UNITED STATES TUNINGBIEANS Bertram Trevor, Riverhead, N. Y., assignor to Radio Corporationof America, a corporation of Delaware Application April 30, 1932, SerialNo. 608,350

9 Claims. (01. 25o-2o) This invention relates to radio signallingsystems and more in particular to systems having means for renderingthem operative over a wide range of frequencies.

Radio signalling systems for operating over a wide range of frequencieshave been known heretofore in the art. For example, 'Brown, UnitedStates Patent No. 1,677,268, shows such a system and in particular areceiver to be used in such a signalling system. In this receiver tocover a broad band of frequencies plug-in coils are used to interconnectthe thermionic amplifiers and to connect the antenna system with thefirst amplifier. Such an arrangement makes possible the use of two ormore sets of tuning coils to be used with a ganged condenser in a radioreceiver. When it is desired to change the frequency band over which thereceiver may be tuned all that is necessary is to plug in a new set ofcoupling inductances.

In arrangements known heretofore of this type considerable diflicultyhas been encountered in that the inductances for interconnecting thecircuits are initially made of like electrical characteristics but wheninserted in the receiver and/or in the shielding compartment thereflected capacity between the coils and adjacent shielded surfaceschanges the effective capacity of the several inductances so that whenthey are connected with a uni-control ganged condenser, each unit ofwhich is of like capacity, the several coupling inductances are not alltuned to resonance for any given setting of the condenser control means.

The above disadvantages have been corrected by the use of equalizingcapacities connected in parallel with the main tuning capacities. Theseequalizing capacities are adjusted to make the total tuning capacity ofeach circuit the same at any main condenser setting. Such an arrangementgives perfect gauging. Such an arrangement, however, is only possiblewhere a single set of tuning coils is to be used.with the gangedcondenser. This ideal condition becomes upset in many instances whereseveral sets of coils are to be used with the same tuning condenser andthe accompanying equalizing condensers, because of a possible change inthe reflected capacity into one or more of the tuned circuits. Inparticular, the tickler coil of the detector in a receiver of this typecouples with the detector tuning inductance or coupling inductance arelatively larger capacity in circuits over certain wave hands whenoperating at high frequencies. An antenna coupling coil could also beanother source of reflecting capacity which might produce differenteffects on the various coupling inductances.

All of the above disadvantages are overcome in the present invention bythe use of several sets of coupling inductances, each inductance ofwhich is enclosed in a separate metallic shield, and each inductance ofwhich is supplied with a separate equalizing condenser connected inparallel therewith. With such an arrangement 10 it is possible to makeevery coil set gang together properly. The ganged condensers with theiradded wiring and fixed equalized capacities must be equalized over thetuning range with no coils connected therein. Each coil set is thenequal- 5 ized with its own set of equalizing condensers as it isconnected or plugged in to give proper ganging without disturbing theequalization of the receiver when the coils are not in place.

The novel features of my invention have been set forth more particularlyin the claims appended hereto.

The nature of my invention and the operation thereof will be understoodfrom the following detailed description and therefrom when read inconnection with the drawings throughout which like reference charactersindicate like parts and in which: l

Figure 1 shows and illustrates the inductance system of the presentinvention, Figure 2 shows one of the inductance units of Fig. 1incorporated in a thermionic receiver.

Referring to the drawings, and in particular to Fig. 1 thereof, S is ashield having several compartments l in each of which is enclosed one ofthe several ganged, tuning capacities C. As shown, each. of thesecapacities has one armature connected to the shield S which may begrounded, and the other armature with a male contact K, the purpose. ofwhich will appear more in detail hereinafter. In order that the tuningcapacity of all of the capacities C may be made equal,

equalizing capacities C1 are connected in parallel with each of the maincapacities C, as shown. All of the capacities C may be adjustedby meansof a single control 4, as indicated. This unit just described isintegral with the receiver proper.

In order to tune the receiver over a wide frequency range each receiveris supplied with a plurality of units each comprising a plurality oftuning inductances L enclosed, as shown in separate compartments 2 in aremovable coil box B. The first of these inductances L is in thearrangement shown adapted to be coupled with a source of high frequencyenergy, as, for'example, an antenna system by means of a couplinginductance L1 coupled through an electrostatic screen 6 to theinductance L. The last inductance L in this system is coupledconductively and inductively with an inductance L3 by means of whichenergy may be fed back from the output of a thermionic detector to theinductance L of this unit. Each inductance L has a female contact 8connected to one terminal, as shown. The contacts 8 are located adjacentopenings 9 with insulating members I!) to permit contacts K to enter theshield B and close the circuit between each inductance L and its tuningcapacity C when the removable coil box B is placed in position on thecompartment S for the tuning condensers. The other terminal of eachinductance L, except the last, is connected as shown at H to the shieldB. The tickler coil L3 associated with the final inductance L also hasone terminal connected at l I, as shown, to the shielded coil box B andthe other terminal connected with a contact I2 cooperating with acontact I 4 which completes a circuit to the detector plate when theremovable coil box B is placed in position on the unit S enclosing theganged condenser.

As pointed out briefly above, the efiective capacity of each main tuningcapacity C can be made equal by means of its associated equalizingcapacity C1. This results that in each position of the control for theganged condenser, the effective capacity of each condenser is the same.However, the receiver might not be tuned to resonance in each circuitover the several frequency bands since, as pointed out above, eachdifferent set of plug-in inductances L might have different reflectedcapacity and result in different total tuning effect for each inductanceunit. This is corrected in accordance with the present invention byproviding for each inductance L a separate equalizing capacity C3. Inpractice, each inductance in each set of tuning inductances L, is tunedby means of its equalizing condenser C3 so that the effective inductanceand capacity of all of the inductances are the same over their tuningrange irrespective of the amount of refiected energy into the detectortuning unit by the tickler coil and/or the capacity reflected into theinductance due to the antenna coupling coil.

In operation, when it is desired to change the frequency over which thereceiver is to be tuned all that is necessary is to position on top ofthe ganged condenser compartment or shield S the removable coil box Bwhich contains the inductances. This is accomplished by merely pluggingthe coil box B into the condenser unit. When in position the contacts Kof the shield S are inserted into the contacts 8 of the box B. Theinsulating members I i) prevent contact between the contact members Kand the metallic shield B.

The equalized inductance systems in the removable coil boxes and thebalanced tuning capacities C and C1 in the unit S may be utilized toconnect or couple together thermionic tubes for relaying or amplifyingradio signals. Any type of coupling may be used. For example, theinductances in the individual containers may be the windings oftransformers, which may be arranged to couple in cascade the thermionictubes, or they may be coupling inductances which cooperate withcapacities to couple the thermionic tubes in cascade by what is known asinductive and capacitive coupling. The inductance system is not limitedto these two types of coupling since, obviously, any combination of theabove types of coupling may be used since the inductance systems of thepresent invention will obviously adapt itself to any type of couplingknown in the art today.

In Figure 2 has been shown an arrangement in 5 which a plurality ofthermionic amplifiers or repeaters are coupled by means of the novelinductance system disclosed in Figure 1. The inductances L, theequalizing condensers C3, and the main tuning capacities C, which areganged, and 10 the balancing capacities C1 are shown as being includedin a single box or container BS. Actually, as indicated above inconection with Figure 1, the' inductances and equalizing condensers arein a separate container which can be replaced with 15 another systemcovering a diflerent range by merely removing the container from theunit S. The input electrodes of tube I 6 are connected with one of theinductances L and its associated equalizing condenser C3 and maincondenser C to 20 tune the input circuit of the thermionic tube Ill tothe desired frequency. The condenser C5 serves as a coupling circuitfilter condenser. Another inductance L and its cooperating equalizingcondenser C3 and main tuning condenser C and its 25 trimmer C1 isinterposed between the source of oscillations or antenna inductance L1and the inductance system LC connected in the input circuit of tube it.In this manner a highly descriminating or selective circuit isinterposed between the input 30 of the first thermionic amplifier andthe signal source L1. IThis insures that only the desired signalpotentials are impressed upon the input electrodes of the tube Hi.

The repeated signal oscillations appearing on 85 the output electrodesof tube It are forced by inductances I through coupling capacities C6 onto another of the inductance system L, C3, from which they aretransferred to a second'inductance A system L, C3, and to the inputelectrodes of the 40 tube l8. These two inductance systems L, C3,interposed between the output of thermionic tube l6, and the inputelectrodes of thermionic tube [2, further insure selectivedescrimination between the desired signals and any undesired signals. Inother words, a receiver coupled as indicated here responds only to thefrequency to which the several inductance systems therein are tuned. Theoutput circuit of tube I 8 is coupled by a single inductance system Land choking inductances I and coupling condenser C6 to the inputelectrodes of a third thermionic amplifier 20, which is in like manercoupled to the input electrodes of a detector 22 and in which thesignals are demodulated and may be utilized from the output circuitthereof in any known manner.

Regenerative action in the detector 22 is insured by coupling the anodethereof through a coupling capacity l5 to the terminal of inductance L3,which is inductively and conductively coupled to the inductance L.Heating current for the filaments of the several tubes is supplied, asindicated, by connecting the terminals AT to the positive terminal of aheating circuit, the negative terminal of which is connected to theshield S and to ground.

Charging potential for the screen grids and anodes is supplied from asource not shown, which has its negative terminal connected to groundand a positive terminal connected to the terminals SG+ and B+.

Biasing potential for the grid electrodes may be supplied from thenegative terminal of a biasing source not shown having its positiveterminal connected to ground by connecting the C leads to said grids tothe negative terminal of said source.

A tuning system, including the equalizing capacities connectedinparallel with each of the plug-in inductances, has been used in ashort wave receiver in which a 6-gang condenser was used with fiveseparate sets of plug-in coils. Each coil set of six coils was built inone container to be plugged into the receiver as a unit, as hereinbeforedescribed. The receiver is operated very efficiently over a range offrom 20,000 to 2500 kilocycles. Although the tuning system has beenshown applied to a receiver, it will be understood that it is notlimited to such use since it may be used in various manners insignalling. For example, such a tuning unit may be used very efficientlyas a band pass pre-selector.

I claim:

1. A radio receiver for receiving signals over a wide band offrequencies comprising a plurality of individually shielded thermionicstages and tuning means interconnecting the stages comprising, ashielded coupling inductance for each stage, an individual equalizingcapacity for each inductance and contained within the shield, a shieldedtuning unit having separate compartments containing a main tuningcapacity for each inductance and an equalizing capacity for each tuningcapacity.

2. A radio receiver comprising a plurality of thermionic stages andtuning means connecting each stage comprising, a plurality ofindividually shielded tuning units each having a plurality of inductancecoils each having effective electrical inductance of substantially likevalue, individual equalizing means contained within the shield for eachinductance coil, and means for synchronously tuning said inductancesincluding a shielded unicontrol tuning unit including an individuallyshielded tuning capacity for each inductance in one of said units and anequalizing capacity contained within the shield for each capacity.

3. A radio receiver comprising a plurality of thermionic tubes, andmeans for coupling said tubes in cascade and for tuning said receiverover a wide band of frequencies comprising a plurality of separateshielded groups, one of said groups having a plurality of inductanceunits each unit including a plurality of inductances of substantiallylike value enclosed in separate shielded conducting chambers, individualtuning means for each inductance contained within the same shieldedconducting chamber, a plurality of main tuning condensers with anadjusting condenser enclosed in a main shield member of another group,said main shield member having contacts projecting therefrom andcooperating with sockets in said inductance units to couple the outputelectrodes of certain ones of said tubes to the input electrodes of afollowing tube, and to connect the output electrodes of other of saidtubes by way of a similar inductive unit to the input electrodes of thefollowing tube.

4. A multi-stage receiver for receiving radio signals over a large bandof frequencies, said receiver being divided into two separate groups ofshielded compartments, one of said groups forming the main tuning andcontrol portion of the receiver, the other group forming the auxiliaryportion of said receiver which comprises a plurality of separate andreplaceable shielded plug-in units, each of the said separatereplaceable shielded plug-in units to cover the desired band offrequencies and comprising a plurality of tuned circuits within shieldedcompartments containing coils of substantially the same inductancevalue, each of the said plug-in units having adjustable capacity meansto alter the tuning of said tuned circuits within the shieldedcompartment, and contact means for each of said shielded compartments tocooperate with corresponding contacts in said main tuning and controlportion to place said receiver in effective operation. 10

5. A radio receiver for receiving signals over a wide band offrequencies comprising a plurality of thermionic stages, tuning meansfor connecting said thermionic stages in a predetermined relationcomprising a coupling inductance for each stage, metallic shieldingmaterial substantially enclosing each coupling inductance and individualequalizing capacity connected with each inductance, said capacity beingcontained within the metallic shielded container, a main tuning unitcomprising a main tuning capacity for tuning said inductance.

6. A radio receiver for receiving signals over a wide band offrequencies comprising a plurality of thermionic stages, tuning meansfor connect- 5 ing said thermionic stages in a predetermined relationcomprising a coupling inductance for each stage, metallic shieldingmaterial substantially enclosing each coupling inductance and individualequalizing capacity connected with each inductance, said capacity beingcontained within the metallic shielded container, 2. main tuning unitcomprising a main tuning capacity for tuning said inductance, andequalizing capacity means connected with each of the tuning 5capacities.

'7. A radio receiver for receiving signals over a wide band offrequencies comprising a plurality of groups of shielded tuning means,each of said groups comprising a plurality of stages at least 9 one ofsaid groups having individually shielded compartments with an inductancein each stage,

a plurality of contacts which are arranged on the outside of saidshielded compartment to contact with at least one or the other groups ofsaid shielded tuning means for the operation of a predetermined band offrequencies within said wide band of frequencies, and individualequalizing capacity shielded with each of the inductances, and containedwithin the individually shielded compartments, a tuning unit havingseparate shielded compartments comprising a main tuning capacity foreach individual inductance and an equalizing capacity for each stage ofsaid tuning capacity.

8. A radio receiver comprising a plurality of individually shieldedthermionic stages and tuning means interposed between adjacent stagescomprising, a plurality of tuning units located within a separateindividually shielded compartment having a plurality of interstagecoupling inductances, individual capacitive tuning means for eachcoupling inductance and contained within the separate shieldedcompartment, a shielded uni-control tuning unit having separatecompartments containing a tuning capacity for each inductance and aseparate equalizing capacity for each tuning capacity.

9. A radio receiver comprising a plurality of thermionic stages andmeans for tuning said "(0 stages over a wide band of frequencies, saidreceiver comprising a first and second separate shielded group, thefirst group comprising a plurality of inductance units'each unitincluding a plurality of inductances of substantially like value,enclosed within a separate shielded chamber, individual capacitivetuning means for each inductance unit, said inductances and individualcapacitive tuning means connected in parallel, a connection from atleast one side of the inductance and the individual capacitive tuningmeans connected to a contact socket which may be plugged into the secondone of said separate shielded groups containing a main tuning con- 10denser comprising, a plurality of condenser units to cover the desiredrange, said condenser units aving contacts projecting from the shieldedgroup and cooperating with the contact sockets connected to theinductance units to complete the interstage coupling circuits when thecircuit of the first shielded group is plugged into the second shieldedgroup containing the plurality of condenser units.

BERTRAM TREVOR.

